The schoolboy, who attends Kingston Academy, has since been told he is not allowed in the store.

A spokesman for the Post Office told the Guardian that it was not a ‘penknife’ and was a standard ‘bottle opener’.

His mum, Lisa Turner, of Beverley Walk, said: “I was mortified.”

“I was heartbroken that they would sell a child a penknife.”

Lisa’s son purchased the £1.69 object on Tuesday 13th January after his grandad, Larry Morgan, gave him some pocket money. Blake told him he was going to the shop to buy a balloon.

“When he came back he said ‘look what I’ve got’ and showed me,” Lisa said.

“I was very upset and asked him what he intended to do with it.”

“I don’t think he understood the dangers but I have spoken to him and so have the police.”

“It scared me.”

A police spokesman has since told this newspaper they are making further enquiries after they were called on 16th January.

Lisa said that discussions have taken place with the Post Office but she said they were ‘abrupt’ and told her not to send her son to the shop again.

“I have had previous arguments with them about selling him energy drinks,” she added.

“I did not get an apology.”

Blake’s grandmother, Carolyn Morgan, said she and her husband Larry were disappointed that their grandson was allowed to buy it.

“To his credit, he told his mum when he came back straight away,” Carolyn said.

“It is out of order, it made us angry. They should not have sold it him.”

Following the claims, the Guardian contacted the Post Office.

A spokesman for the Post office said: “We would like to clarify that the item in question was a standard ‘bottle opener’ not a ‘penknife’.”

“In this instance, the child stated that his mother required the bottle opener. The police have stated that there is no case to answer although they did offer advice over the sale of such items for future.”